For questions like this, examples would help. (They're probably in your textbook.)

Terminology is used differently in different theories (and textbooks!), and definitions are extremely important for giving the right answer. That said, you can also search online (Wikipedia usually has an article) for the most common use of the terminology with examples.

Is an "element clause" one that begins with "that" and acts like a noun? ("That I had ice cream pleased me.") I'm not sure how that would be either adverbial or predicative. Or maybe "element clause" just means "a clause that is an element of another clause", in other words an embedded clause? In that case, adverbials would be things with normal subordinating conjunctions ("because", "when", etc.), and a predicative use would I guess be when it's the object of a verb, like "I know that you are studying linguistics".

Starting with the definitions is important, like how "adverbial" or "predicative" is defined in your textbook. The rest should work out after you have figured out the constituent structure of the sentence.